When the voltage is reduced, the motor, as the core device of electric drive, will experience a series of significant changes. The following is a detailed analysis of these changes to help better understand the impact of voltage reduction on motor performance and operating status. 1. Current Change Principle: According to Ohm's law , the relationship between current I, voltage U and resistance R is I=U/R. In a motor, the resistance R (mainly stator resistance and rotor resistance) usually does not change much, so a decrease in voltage U will directly lead to an increase in current I. For different types of motors, the specific manifestation of current change may be different. Specific performance: DC Motors: For brushless DC motors (BLDC) and brushed DC motors, the current will increase significantly when the voltage is reduced, provided the load remains the same. This is because the motor requires more current to maintain the original torque output. AC motor: For asynchronous motors, although the motor will automatically reduce speed to match the load when the voltage is reduced, the current may still increase when the load is heavy or changes rapidly. For synchronous motors, when the voltage is reduced, if the load remains unchanged, the current theoretically does not change much, but if the load increases, the current will also increase. 2. Changes in torque and speed Torque change : A voltage reduction usually results in a reduction in motor torque. This is because torque is proportional to the product of current and magnetic flux. When the voltage is reduced, although the current increases, the magnetic flux may decrease due to insufficient voltage, resulting in a decrease in overall torque. However, in some cases, such as in DC motors, if the current increases enough, it may compensate for the decrease in magnetic flux to a certain extent, keeping the torque relatively stable. Speed change : For AC motors, especially asynchronous motors and synchronous motors, a voltage reduction will directly lead to a reduction in speed. This is because the motor speed is related to the power supply frequency and the number of motor poles , and the voltage reduction will affect the electromagnetic field strength of the motor, thereby reducing the speed. For DC motors, the speed is proportional to the voltage, so when the voltage is reduced, the speed will also decrease accordingly. 3. Efficiency and heat generation Reduced efficiency : A reduced voltage will result in a reduced motor efficiency because when the motor runs at a lower voltage, it requires more current to maintain output power, and the increase in current will increase the copper and iron losses of the motor , thereby reducing the overall efficiency. Increased heat : Due to the increase in current and the decrease in efficiency, the motor will generate more heat during operation. This will not only accelerate the aging and wear of the motor, but may also trigger the activation of the overheating protection device, causing the motor to shut down. 4. Impact on motor life Long-term operation in an environment with unstable voltage or too low voltage will seriously shorten the service life of the motor. The increase in current, torque fluctuation, speed drop and efficiency reduction caused by the voltage reduction will damage the internal structure and electrical performance of the motor. In addition, the increase in heat will also accelerate the aging process of the motor insulation material. V. Countermeasures To mitigate the impact of voltage reduction on the motor, the following measures can be taken: Optimize the power supply system: ensure the voltage stability of the power supply grid to avoid voltage fluctuations causing shocks to the motor. Choose a suitable motor: fully consider the voltage fluctuation factor during design and selection and choose a motor with a wider voltage adaptability range. Install a voltage stabilizer: Install a voltage stabilizer or voltage regulator at the motor input to maintain voltage stability. Strengthen maintenance: Regularly inspect and maintain the motor to promptly detect and address potential problems to extend the service life of the motor. In summary, voltage reduction has many effects on motors, including current changes, torque and speed changes, efficiency and heating issues, and the impact on motor life. Therefore, effective measures need to be taken in practical applications to mitigate these effects and ensure safe and stable operation of the motor.
XINDA